Studies are in progress to determine the role of properdin in systemic lupus erythematosus. The studies have thus far revealed that properdin and Factor B are present in the glomerular basement membrane of some patients with lupus nephritis. Studies of lesional skin from these patients reveals that these proteins are infrequently present at the dermal-epidermal junction. Additional tissue from involved and uninvolved skin from patients with chronic discoid lupus are in progress. Levels of circulating complement components, Factor B and properdin will be correlated with the presence of these proteins in skin and kidney.